JPH08213717A - FEL device wavelength switching method - Google Patents

Abstract

(57) [Summary] [Object] To provide a method for continuously and automatically switching desired wavelengths of an FEL device, which has the advantage of continuously variable wavelengths. Constitution: In an accelerator 1'having an undulator 7 on an electron storage ring 2, a monitoring monitor head 18 is provided for the emitted light 2 ", a magnetic field measurement controller 23 is provided on a deflection electromagnet 6, and the undulator 7 is further provided.
Button electrodes 11 and 11 for beam position monitoring are provided before and after, and the tune and the magnetic field strength of the deflection electromagnet are automatically recognized through the electromagnetic applied current control computer 15, and the tune of the optimum wavelength and the power control of the FEL are performed. To be able to. [Effect] The FEL wavelength can be continuously tuned and the power can be freely set as desired, the original merit of the FEL device can be smoothly utilized, and a practical industrial photon can be realized.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The disclosed technology belongs to the technical field of an algorithm for setting the wavelength of FEL in an electron storage ring accelerator that emits SR light or FEL continuously and automatically.

[0002]

2. Description of the Related Art As is well known, lasers are used in various industries, medicine, chemistry and biotechnology, and they may be used in the most advanced fields such as group separation and nuclear fusion in the future. Electron lasers) have various advantages such as their wavelengths being continuously variable from the visible region to the far infrared region, and many research institutions and companies have received special attention, and various studies have been conducted earnestly. However, various necks lie in the emergence of FEL devices as so-called industrial photons, and one of them is the FEL device.
The characteristic of the inherent merit that the wavelength of is continuously variable may not be set automatically as desired, and in each research period, etc., only various researches have been done on the wavelength set specifically, , NUCLER INSTR
UMENTS AND METHODS IN PHYSICS RESEARCH (1993) ABS34-
The ABS39 reference only indicates that the wavelength of the spontaneous emission can be switched intermittently by manual operation by changing the undulator gap.

Thus, in order to switch the wavelength of the FEL, the method of changing the energy of the electron beam accumulated in a ring shape and the magnetic field intensity on the beam orbit of the undulator (change of the undulator gap) Etc.) and a method combining both of them are theoretically known.

[0004]

However, in any of the methods, when the change is made, a tune shift occurs due to a change in the vertical focusing force of the undulator, the setting of the storage ring is changed, and when the change becomes large, the beam is changed. Is unstable, the life of the beam is shortened, and in the extreme case, the beam itself is lost.

In the arrangement of the electromagnets provided on the electron beam storage ring, C.I. G. The TBA lattice type and TBA lattice type may have different magnetic field settings even if they are the same tune, and it is only necessary to confirm the current value applied to the deflecting electromagnet when changing the beam energy to the magnetic field. The problem is that reproducibility cannot be guaranteed.

In the operation so far, the energy of the accumulated electron beam is monitored to detect only the current value applied when the deflection electromagnet is operated (for example, the invention disclosed in JP-A-5-47500). Since the wavelengths are switched only by the operation, there is a problem that a tune shift and a COD (closed beam orbit) shift occur, and an appropriate setting cannot be made.

Therefore, an experimental operation is performed in which a tune condition is given to a special wavelength and the magnetic field strength of the bending electromagnet is appropriately controlled, and the operation is smooth and automatic.
Moreover, there is a disadvantage that the wavelengths cannot be continuously switched.

Covering, the wavelength λ of FEL is

[0009]

[Number 1] _{λ = λ w (1 + K} 2/2) / 2γ 2 K = 93.4B · λ w However, lambda is the wavelength of the FEL, lambda _w is the period length of the periodic magnetic field undulator, K is Ange The value is proportional to the magnetic field strength of the lator, B is the peak magnetic field strength, and γ is the electron energy divided by the rest mass of the electron.

The FEL wavelength is determined by the energy of the electron and the intensity of the periodic magnetic field of the undulator, and in order to switch smoothly, it is necessary to control the magnetic field intensity of the undulator and the electron energy with high precision. is there.

However, in the electron storage ring, the energy of the electrons is determined by the magnetic field strength of the deflection electromagnet, and the magnetic field strength of the deflection electromagnet is controlled by the value of the current that is normally applied. When the wavelength is set to, the magnetic field strength is not guaranteed due to the hysteresis of the electromagnet, and therefore the magnetic field strength of the deflecting electromagnet cannot be controlled accurately, so that there is a demerit that the switching of the FEL wavelength cannot be smoothly controlled. It was there.

Further, since the power of the FEL is determined by many parameters such as the energy of accumulated electrons, the reflectance of the mirror, the transmittance of the mirror, the direct method is currently the best method.

[0013]

OBJECTS OF THE INVENTION The object of the invention of this application is the FEL based on the above-mentioned prior art, which has an inherently excellent continuous tunability of wavelength.
It is theoretically understood that the technical problem to be solved is a problem that cannot set continuously switching desired wavelength, which is a neck of practical industrial photons while having the advantage of the device. To be able to put into practical use either the method of changing the energy of the electron beam, the method of changing the magnetic field intensity on the beam orbit of the undulator (changing the undulator gap, etc.), or the combination of both. In any of the methods, tune shift is prevented from occurring due to the change of the vertical focusing force of the undulator, and for COD (closed orbit of the beam), beam position monitoring is performed with a button electrode or the like to detect the beam position. Measurement is performed, calibration data regarding wavelength is created in advance, and is input to the control computer. While further correcting the tune and COD (beam closed orbit) according constant algorithm control, to be able to switch the wavelength continuously,
As a result, it is possible to smoothly switch desired FEL wavelengths and to control FEL power, thereby providing an excellent FEL device wavelength switching method that is useful in various fields of electronic energy technology application. To do.

[0014]

In order to solve the above-mentioned problems, an electron storage ring for emitting SR light or FEL is provided in order to solve the above-mentioned problems. In the accelerator provided with the undulator, in order to stabilize the electron beam accumulated with respect to electron energy when continuously switching the wavelength of the FEL as desired, in order to stabilize the tune of the parameter, the emitted light of the beam is fixed. Is received by a photodiode or the like to be converted into an electric signal, and the electric signal is constantly monitored by Fourier analysis by an FFT analyzer to be used as a probe.

Then, in the electron storage ring, the magnetic field of the deflecting electromagnet is constantly measured by a Hall element or a magnetic field measuring device such as NMR for the stored electron energy, and used as a probe.

Further, the magnetic field strength of the undulator is controlled by changing the distance between the magnets installed above and below by driving a motor, and the COD (closed orbit of the beam) correction is monitored by button electrodes for beam position monitoring. The beam trajectory is calibrated by the correction coil using.

Regarding the method of switching the wavelength, there are a method of changing only the energy of the stored electrons, a method of changing only the magnetic field of the undulator, and a method of changing both the energy of the electron and the magnetic field of the undulator. Further, regarding the above-mentioned three measurement control systems, according to a predetermined algorithm via a computer, the wavelength switching and the FEL power control are performed by calculating according to the data table of the measurement wavelength pre-input to the computer. It is a technical measure that has been taken.

[0018]

Embodiments of the invention of this application will be described below with reference to the drawings.

In the embodiments shown in FIGS. 1 and 2, reference numeral 1 is a storage ring type accelerator for radiating SR light or FEL having a function used in the FEL wavelength switching method, which is the center of the invention of this application, The electron storage ring 2 faces the septum electromagnet 3 obliquely with an incident path 4 of electrons emitted from a linac (not shown), and subsequently, a quadrupole electromagnet 5, a deflection electromagnet 6 and the like are arranged in a race track shape. An undulator 7 is set on an extension washing of a predetermined midway portion and oscillation mirrors 13 and 13 are set, a quadrupole electromagnet 5, a deflection electromagnet 6 and the like are further installed via a kicker electromagnet 8, and an RF cavity 9, Also, the RF knockout electrodes 10 are arranged in a predetermined manner.

Immediately before and after the undulator 7, button electrodes 11 and 11 which are known to be used for monitoring COD (closed orbit of beam) are provided, and an electron beam position detector (detector etc.) 14 is provided. And to each electromagnetic application current control computer 15.

The RF output from the FFT analyzer (including the tracking generator) 17 is connected to the RF knockout electrode 10 via the amplifier 16, and R
It is electrically connected to the control computer 15 for reading the E-analyzer data.

A tune monitoring head 18 is provided for the emitted light from the deflection electromagnet 6 provided at the subsequent stage of the septum electromagnet 3 and is connected to the FFT analyzer 17.

In order to maintain the stability of the accumulated electron beam 2 ', it is necessary to fix the tune parameters as described above. The known tune monitoring construction is shown in FIG. As shown, emitted light (electrons) emitted from the electron beam 2'from the deflection electromagnet 6
2 ″ is input to the divided photodiode 26 via the reflection mirror 12 and the focus lens 25, is electrically converted, and the output is amplified by each amplifier 27. After passing through the difference amplifier of the output of each divided diode, left and right FFT analysis is performed by the FFT analyzer 29 through the directional tune amplifier 27 ′ and the vertical tune amplifier 27 ″.

RF corresponding to tune for the beam
To give resonance to the tracking generator 28.
After passing through the amplifier 27, one side of the output is output to the phase controller 30 and the other side is directly output to the amplifier 27 so that the RF oscillation can be efficiently supplied to the beam vertically or horizontally.

As described above, the beam is oscillated by the RF knockout, and the oscillation resonating with the oscillation is detected by the photodiode and FFT-analyzed, so that it can be constantly monitored and used as a tune probe.

Then, the following data signals are inputted from the respective electromagnetic applied current control computers 15 to the deflecting electromagnet power supply 19, the quadrupole electromagnet power supplies 20, 21, 22 and the correction coil 22 ', and the electromagnets are supplied to the electromagnets. It is transmitted to the correction coil.

In this way, the emitted light 2 of the electron beam 2'is
'' Is used as a tune probe by constantly performing Fourier analysis of the electric signal of the photoelectric conversion element through the photodiode 26 and photoelectric conversion through the FFT analyzer 29.

However, the tune is controlled by controlling the applied current values of the quadrupole electromagnets for focusing and defocusing, and is kept constant.
In an electron storage ring having three types of quadrupole electromagnets depending on the type of arrangement of electromagnets such as A and TBA, the magnetic field of the third quadrupole electromagnet for focusing in the lateral direction that determines the size of the beam due to stored electron energy dispersion The intensity also needs to be monitored by the magnetic field measuring device, because even if the values are the same tune, different beam parameters have different beam parameters.

In order to deal with this, a well-known Hall element or N in the deflection electromagnet 6 as a probe of the energy of the electron beam accumulated in the accumulation ring as in the embodiment shown in FIG.
The magnetic field measuring device 24 such as MR is permanently installed and electrically connected to each electromagnetic applied current control computer 15 via the deflecting electromagnet controllers 23 and 23 'to be used as a probe.

In the case of using a permanent magnet, the magnetic field strength of the undulator is controlled by driving the distance between magnets through which the beam passes by a motor or the like and measuring and controlling the gap distance by an encoder or the like. .

As described above, four measurements of the magnetic field, the undulator gap, the tune, and the COD (closed orbit of the beam) and the control are performed, calibration data regarding the control is prepared, and the tune is performed according to a predetermined algorithm based on the calibration data. While further correcting COD (closed orbit of beam), the wavelength of FEL is gradually changed.

Therefore, as shown in Table 1 below, as many wavelengths as possible when the respective parameters are changed are prepared, and each wavelength is measured using a spectroscope or a monochromator. These data are input into the data bank of the computer in advance.

Further, the relationship between the accumulated current value of each wavelength and the FEL power is also measured by using a current monitor (DCCT) and a photodiode, etc., and input to the data bank.

[0034]

[Table 1] Next, the means for switching the wavelength of the FEL is basically a means for changing only the energy of the stored electrons, a means for changing only the magnetic field of the undulator, and a means for changing both the energy of the stored electrons and the magnetic field of the undulator. Then, algorithms for these means will be described below with reference to FIGS. 4, 5 and 6.

First, a chart of wavelength switching by changing only energy is shown in FIG. 4, where the current wavelength λ ₁ and
The magnetic field strength B ₁ (or energy) of the deflecting electromagnet 6 is input to the computer (substantially only two parameters of wavelength and magnetic field strength undulator gap are required), or the magnetic field strength of the third quadrupole electromagnet. After monitoring and checking that there is no value shift, the wavelength λ ₂ to be newly switched and set, and the magnetic field strength B ₂ corresponding to this wavelength are input to the computer as described above in Table 1 of the measurement wavelength. Calculated from the data table of.

Next, the change width ΔB per time is input.

Then, the tune is monitored to adjust the values of the focus and both quadrupole electromagnets of the focus, and the energy is gradually changed while performing COD (beam closed orbit) correction.

Then, in this case, the step value for changing each parameter uses the value interpolated in the measured data table of Table 1, and when the correction of tune or COD (closed orbit of the beam) exceeds the tolerance, The values are corrected by the correction loop of 1. and each corrected value is recorded as correction data from λ ₁ to λ ₂ .

Finally, the magnetic field strength is changed to B ₂ to end the continuous switching of the wavelength.

Next, the flow chart of wavelength switching by changing only the undulator gap is shown in FIG.
The current wavelength λ ₁ and the magnetic field strength B ₁ (or energy) of the bending electromagnet 6 are input to the computer (in this case also, the wavelength, the magnetic field strength, and the undulator gap are substantially the same). 2 out of
Only one parameter is required), and the third quadrupole electromagnet 5
After checking the magnetic field strength of the and confirming that there is no value shift, enter the wavelength λ ₂ that you want to set next into the computer and set the undulator gap corresponding to this to the interval h ₂ entered in the computer in advance. 1
It is calculated from the data table of the measurement wavelength of.

Next, the change width Δh per time is input, and then only the undulator gap Δh is changed.

When the correction of tune or COD (closed orbit of the beam) exceeds the tolerance, the value is corrected by each correction loop, and each corrected value is corrected data from λ ₁ to λ ₂ . Data is recorded as.

By repeating the above steps, the value of the undulator gap is changed to h ₂ and the wavelength switching is completed.

Next, the algorithm for the wavelength switching chart for changing both the energy and the undulator gap is as shown in FIG. 6, and the current wavelength λ ₁ and the magnetic field strength of the deflection electromagnet are the same as the above algorithm. B ₁ (or energy) is input to the computer 15 (substantially similarly, only two parameters of the wavelength magnetic field intensity undulator gap are required).

Also, after monitoring the magnetic field strength of the third quadrupole electromagnet 5 and checking that there is no value deviation,
Next, the computer 1 sets the wavelength λ ₂ and the undulator gap value h ₂ or the magnetic field strength B ₂ to be set.
5, and the magnetic field strength B ₂ of the deflection electromagnet or the undulator gap interval h ₂ corresponding thereto is calculated from the data table of the measurement wavelength of Table 1 which is input in the computer in advance.

Then, each change width Δ
Input h and ΔB.

Next, the undulator gap is changed from h ₁ to Δh, and when the correction of tune or COD (closed orbit of the beam) exceeds the tolerance, the value is corrected by each correction loop, and each is corrected. The modified value of is λ ₁
Data is recorded as the correction data from λ ₂ to λ ₂ .

Similarly, COD (closed orbit of beam) and tune are corrected in the correction loop, and data is recorded in the same manner.

By repeating the above steps, the value of 6 of the deflecting electromagnet is changed to B ₂ and the value of the undulator gap is changed to h ₂ to complete the wavelength switching.

In the above three modes, when the wavelengths are switched more continuously and smoothly, the data corrected by the above-mentioned trial is used. In this case, COD (closed orbit of beam) and tune need to be corrected. This is useful for improving the processing speed because there is no such problem.

In this way, the switching setting of the FEL wavelength can be continuously, automatically and smoothly performed as quickly as possible.

In particular, if the method of changing both the energy and the undulator gap is used, the current accumulated current value is input and the energy and the undulator gap change value during wavelength switching are obtained as FEL output data at each wavelength. By making the determination in consideration, for example, it becomes possible to perform wavelength switching such that a constant FEL output is obtained during wavelength switching.

Of course, the embodiment of the invention of this application is not limited to the above-mentioned embodiments. For example, the PID control is used for the tune correction loop or the COD correction loop independently or continuously. A method is also conceivable in which the wavelength is corrected and the loop is made to function, and independently of that, the wavelength is changed by the above-mentioned three methods.

[0054]

As described above, according to the invention of this application, basically, the energy of the electron beam accumulated in the ring is changed for the wavelength switching of the FEL which has the excellent advantage that the wavelength is continuously variable. Method and undulator gap changing method to change the magnetic field strength of the undulator,
In addition, although three modes such as a combination of both are theoretically considered, in reality, while monitoring the energy of the electron beam accumulated in the ring and recognizing only the applied current value of the deflection electromagnet, Since the tune was changed manually, it was not possible to subtly respond to changes in the tune, COD (closed orbit of the beam), etc., and smooth switching was not possible because of the magnetic field gap, tune,
COD (closed orbit of beam) is measured and controlled, calibration data regarding wavelength is created, and based on the calibration data, tune and COD are performed according to a predetermined control algorithm.
Since the wavelength can be gradually changed while adjusting the (beam closed orbit), the desired switching of the wavelength is extremely smooth and automatically and continuously, and the FEL output can be controlled. The excellent effect that it can be performed is exhibited.

[Brief description of drawings]

FIG. 1 is a schematic mechanism diagram of one embodiment of the invention of this application.

FIG. 2 is a schematic mechanism diagram of the tune monitoring of FIG.

FIG. 3 is a schematic mechanism diagram corresponding to FIG. 1 of another embodiment.

FIG. 4 is a flowchart of an algorithm of a wavelength switching chart when only energy is changed.

FIG. 5 is a flowchart of an algorithm of a wavelength switching chart when only the undulator gap is changed.

FIG. 6 is a flow chart diagram of the undulator of the wavelength undulator chart by changing the undulator gap and the energy.

[Explanation of symbols]

1 FEL device 2 Electron storage ring 2'Beam 2 '' Synchrotron radiation 3 Septum electromagnet 4 Beam incident path 5 Quadrupole electromagnet 6 Deflection electromagnet 7 Undulator 8 Kicker electromagnet 9 RF cavity 10 RF knockout electrode 11 Button electrode 12 Reflection mirror 13 FEL resonance Mirror 14 Beam position detector (detector etc.) 15 Control computer 16 Amplifier 17 FFT analyzer (including tracking generator) 18 Tune monitoring head 19 Deflection electromagnet power source 20, 21, 22 Quadrupole electromagnet power source 22 'Correction coil power source 23, 23 'magnetic field measuring device controller 24 magnetic field measuring device 25 focus lens 26 split photodiode 27 amplifier 27' difference amplifier 28 tracking generator 29 FFT analyzer 30 phase Controller

Continued front page (72) Masayuki Kawai 1-1 Kawasaki-cho, Akashi-shi, Hyogo Prefecture Kawasaki Heavy Industries Ltd. Akashi factory (72) Inventor Shinji Hamada 1-1 Kawasaki-cho, Akashi-shi, Hyogo Akashi Kawasaki Industry Co., Ltd. Inside the factory (72) Inventor Tetsuo Yamazaki 1-4-1, Umezono, Tsukuba-shi, Ibaraki Industrial Technology Research Institute (72) Inventor Yamakazu Iwakatsu 1-4-1, Umezono, Tsukuba-shi, Ibaraki Industrial technology Inside Institute of Electronics Technology

Claims (5)

[Claims] 1. A FEL while recognizing operating parameters of an FEL device having an undulator in an electronic storage ring.
In the wavelength switching method of the FEL device which sets the wavelength of the FEL to a desired value, the FEL wavelength is continuously determined for a predetermined time by monitoring the tune of the electron orbit and the COD (closed orbit of the beam) of the undulator. A wavelength switching method for an FEL device, characterized in that a desired setting is made in the device. 2. A FEL while recognizing operating parameters of a FEL device having an undulator in an electronic storage ring.
In the wavelength switching method of the FEL device for setting the desired wavelength, the tune of the electron orbit is monitored, the COD (closed orbit of the beam) of the undulator is monitored, and the magnetic field of the electromagnet interposed in the electron storage ring is further monitored. A wavelength switching method for an FEL device, characterized in that the wavelength of the FEL is continuously set within a predetermined time by monitoring. 3. The wavelength switching method for an FEL device according to claim 1, wherein the tuned monitoring is performed on the emitted light of the beam through a photodiode. 4. A calibration data table for wavelengths is created for each of the above monitorings, and the wavelengths are gradually switched while correcting the monitoring data according to a control algorithm based on the calibration data table. 5. A wavelength switching method for an FEL device according to any one of items 1 and 2. 5. A wavelength switching method for an FEL device, wherein the calibration current is added to the accumulated current value and FEL power data to control the FEL power during wavelength switching as desired.